1. Field of the Invention
This invention relates to a blockade seal, and more particularly, to a blockade seal for use for sealing an envelope or as a light shielding seal of a ROM.
2. Description of the Prior Art
Conventionally, a blockade seal to be attached to an envelope of the registered mail has been used. The blockade seal is intended to prevent a third person from opening the envelope containing, for example, cash. Further, a blockade seal to be attached to an envelope containing an important document, a blockade seal to be attached to the CPU control box of a pinball machine, a blockade seal for light shielding of a ROM and the like have been used to protect a content located inside thereof. Some types of these blockade seals are printed in individual manners to indicate that the blockade seals have their own purposes or for identification.
However, because the conventional blockade seals are produced by printing on the sheets, such blockade seals can be forged easily. Additionally, these blockade seals are attached to envelopes by adhesive, and they can be removed easily without leaving a trace of such removal. If such a trace of the removal is not seen, it is impossible to make sure whether a blockade seal was attached initially, so that a third person can open the envelope without such unauthorized opening being detected by others. Further, when the blockade seal is forged, if that forged blockade seal is attached after a proper seal is removed and an envelope is opened, it is impossible to make sure that the envelope was kept confidential.